The rapid development of the Internet technology enables rich and colorful services to be provided for users, but many Internet services involve the problem of personal information security. In order to protect the security of personal information, the most common method is to use password. For example, a user is required to remember the password of each client when he logs in a client (instant messaging tool, email address, on-line game and forum community), which is rather difficult and troublesome for users. In order to remember them easily, many users set their passwords as easy and regular contents, and even set a same password for multiple client accounts, which greatly reduces the security of password. In order to enhance the security, it is desirable that a password is set meaningless, and constructed with longer content combined with multiple kinds of characters, signs and numbers; nevertheless such a password is difficult to remember.
For the conflict between the password security and easy to remember, some existing application software and browsers provide additionally automatically remembering passwords as well as the function of automatic login through a memorized password. However, a user still has to set and manage the password of each client, which is also quite troublesome. Therefore, software for unified management of username and passwords has been provided, through which a user can log in a client automatically with the user name and password under unified management. However, the passwords are usually stored in local hard disks for both of the above mentioned automatic login methods, and no strict identity authentication measures are taken; once a user's PC is available to another one, he can also get access to the stored accounts and passwords, bringing certain potential security problems.
Therefore, it is urgent now to find a method for automatically logging in a client so as to improve the security during automatically logging in a client.